It is because aio-last-ref-held-by-io uses a static buffer that is been usedrepeatedly for every io_submit() call, but we'll issue NUM_IOS(=16) io_sumbit()in a 'for' loop at a time, and when those data read by aio has not finish itsendio(), its memory is likely to be used in the next io_submit, which ends updata corruption and numerous checksum errors.

This allocates memory for each io_submit() and generic/323 runs fine after this.